Unvented Finished Attic Insulation

A fundamental requirement of an unvented attic assembly is the use of air impermeable insulation on the underside of the unvented roof to prevent air infiltration and exclude airborne moisture from the attic.

Unvented finished attic insulation. The advantages of unvented attic construction using spray foam insulation are numerous. This document provides a brief description of different types of unvented roof assemblies and the benefits of unvented roof construction. Proper attic insulation is the best way to prevent heat loss in the winter and retain cool air in the summer. Un vented hot roof designs indoors finished attic.

The unvented attic space is completely within the building thermal envelope. Insulation approaches for unvented attics vary by climate. This reduces latent air conditioning loads and provides further reductions in energy consumption. These assemblies are created by eliminating ventilation openings and moving the thermal moisture and air control boundaries to the plane of the roof deck.

To provide an unvented conditioned space for locating hvac equipment in the attic and or to provide a continuous thermal barrier for designs that have complex coffered ceiling planes and or numerous penetrations for lights speakers vents soffits etc which make it difficult to achieve an airtight ceiling plane. The roof insulation and air barrier must follow the plane of roofing materials rather than diverge figure 2. Fibrous insulation fibrous insulation e g batt or blown in can be installed under the roof deck in the hot dry. This allows you to install your bulkheads above the ceiling plane without the need for spray foam insulation.

Unvented roof assemblies should be insulated either with air impermeable insulation rigid foam or spray polyurethane foam or with a combination of foam and air permeable insulation. If you don t want to use sips or nailbase there are four basic approaches. Install insulation along the underside of the roof deck of an unvented attic rather than on the ceiling deck of a vented attic for either of two reasons. So it s time to pay close attention to what s happening up there.

It is a proven cost effective approach to creating a more energy efficient building particularly when the hvac system is located in the attic space. An alternate to spray foam insulation in an unvented attic is plenum trusses which allow you create a reverse bulkhead above the ceiling plane that is insulated. Four options for building an unvented roof assembly.